Acyltransferase activities in adult rat type II pneumocyte-derived subcellular fractions

• Published in: Biochimica et biophysica acta Vol. 795; no. 2; pp. 238 - 246
• Main Authors: Crecelius, Charles A., Longmore, William J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 12.09.1984; Elsevier; North-Holland
• Subjects: Acyltransferase; Acyltransferases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cells, Cultured; Cytosol - enzymology; Fundamental and applied biological sciences. Psychology; Glycerolipid metabolism; Kinetics; Lipids; Lung - cytology; Lung - enzymology; Lung surfactant; Male; Microbodies - enzymology; Microsomes - enzymology; Mitochondria - enzymology; Other biological molecules; Phospholipids - metabolism; Rat lung; Rats; Rats, Inbred Strains; Type II cell; Rat lung; Lung surfactant; Acyltransferase; Type II cell; Glycerolipid metabolism; Pneumocyte; Vertebrata; Mammalia; Rat; Pulmonary surfactant; Lung; Rodentia; Lipids; Localization; Microsome; Metabolism
• ISSN: 0005-2760; 0006-3002; 1879-145X; 1878-2434
• DOI: 10.1016/0005-2760(84)90071-7

1. 1. Acyl-CoA: lysophosphatidylcholine, acyl-CoA: lysophosphatidylethanolamine, and lysophosphatidylcholine: lysophosphatidylcholine acyltransferases were investigated using subcellular fractions derived from adult rat type II pneumocytes in primary culture. Acyl-CoA: lysophospholipid acyltransferase activities were determined to be microsomal, while lysophosphatidylcholine: lysophosphatidylcholine acyltransferase activity was found to be cytosolic. Total palmitoyl CoA: lysophosphatidylcholine acyltransferase activity was 30-fold greater than lysophosphatidylcholine: lysophosphatidylcholine acyltransferase activity, indicating that the former enzyme is more important in the synthesis of dipalmitoyl phosphatidylcholine. 2. 2. Palmitoyl-CoA and oleoyl-CoA lysophosphatidylcholine acyltransferase activities were approximately equal under optimal substrate conditions. Specific activities of the enzyme using arachidoyl-CoA and arachidonoyl-CoA were 46% and 18%, respectively, of those with palmitoyl-CoA. Acyl-CoA: lysophosphatidylethanolamine acyltransferase showed a preference for palmitoyl-CoA as opposed to oleoyl-CoA under optimal conditions. However, when equimolar concentrations of either palmitoyl-CoA and oleoyl-CoA or palmitoyl-CoA and arachidoyl-CoA were assayed together, the relative utilization of the two substrates was found to be dependent on total acyl-CoA concentration. At higher concentrations, the incorporation of palmitoyl-CoA into phosphatidylcholine was less than other acyl-CoAs. However, at lower concentrations palmitoyl-CoA was utilized quite selectively. Whole lung microsomes did not show as marked a preference for palmitoyl-CoA as did type II pneumocyte microsomes under these same conditions. In similar experiments, low total acyl-CoA concentrations produced greater incorporation of oleoyl-CoA into phosphatidylethanolamine. For both enzymes total activity at the lowest concentrations used was at least 45% that at optimal conditions. This demonstrates that the type II pneumocyte acyltransferase system(s) can selectively utilize palmitoyl-CoA. 3. 3. No evidence for direct exchange of palmitoyl-CoA with 1-saturated-2-unsaturated phosphatidylcholine in subcellular fractions from type II pneumocytes was found.